Important Points
Potentiometer is an ideal voltmeter . Sensitivity of potentiometer is increased by increasing length of potentiometer wire .
If n identical resistances are first connected in series and then in parallel . the ratio of the equivalent resistance .
Rs / Rp = n 2 / 1
If a skeleton cube is made with 12 equal resistance , each having a resistance R , then the net resistance across
1 . The diagonal of cube = 5 / 6 R 2 . The diagonal of a face = 3 / 4 R 3 . along a side = 7 / 12 R
If a resistance wire is stretched to a greater length , keeping volume constant , then
R ∝ l 2 ⇒ R1 / R2 = ( l1 / l2 ) 2 and R ∝ 1 / r 4 ⇒ R1 / R2 = ( r2 / r1 ) 4
where l is the length of wire and r is the radius of cross-section area of wire .
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